Preheat your oven to 350°F. In a medium bowl, combine the gluten-free graham cracker crumbs, ⅓ cup of granulated sugar, and melted butter. Mix until well combined. Press the mixture into a 9-inch pie pan and bake for 8-10 minutes until lightly golden. Let it cool completely.

In a medium saucepan, whisk together 1 cup of granulated sugar and ⅓ cup of cornstarch. Gradually add 1 ½ cups of water, stirring until smooth. Cook over medium heat, stirring constantly until thickened and boiling.

In a separate bowl, whisk the 4 egg yolks. Slowly add about 1 cup of the hot mixture to the egg yolks, whisking constantly. Pour the egg mixture back into the saucepan and cook for an additional 2-3 minutes until thickened. Remove from heat and stir in lemon zest, lemon juice, 2 tablespoons of butter, and vanilla extract.

In a mixing bowl, pour in 1 cup of heavy whipping cream and add 2 tablespoons of powdered sugar. Whip on medium speed until soft peaks form.

Pour the lemon filling into the cooled crust and smooth the top. Refrigerate for at least 4 hours until set. Spread or pipe the whipped cream over the filling and garnish with lemon slices and mint leaves if desired.